Does the length of a car ownership really cut both ways? Not really, according to an analysis by 24/7 Wall St. The relationship between the length of car ownership and loyalty is weak at best.

Based on data provided by Edmunds.com, 24/7 Wall St. examined the 30 largest brands sold in the United States measured by unit volume to find the average length of car ownership for each make. The brands people hold for long periods have several characteristics in common.

Most sell very few units and therefore have a small market share. Jaguar owners hold their cars for seven years, but in a good month the brand sells just 1,000 units. Similarly, Volvo and Mitsubishi — also high on our list for years of ownership — sell around 4,000 units per month.

In an interview with 24/7 Wall St., Edmunds.com analyst Jeremy Acevedo explained that shrinking market share also plays a major role in the age of traded-in vehicles. In several cases, the fact that far fewer of these vehicles are being sold today means the average age of those vehicles is necessarily going to be older.

Sales of seven of the nine makes on our list declined by more than 20% between 2007 and 2011. Sales of Mitsubishi dropped by 38.6% during that period, while sales of Chrysler sank by nearly 60%.

Another common factor among these brands is the relatively older age of the car owners. Acevedo explained, “frequently, it’s just a prudent fiscal decision to hang on to your car for longer.”

It is likely that this decision is especially important for seniors because “driving is less of an imperative, if they’re retired they may not be driving around as much as younger drivers.”

While the national average age for car owners is 51, the average age of a Lincoln owner is 60. Of course, parent Ford would like to bring that down. Buick owners are not that much younger, at 59 years old. Jaguar, formerly owned by Ford, and Chrysler owners are about 55 years old.

Some correlations are clear but hard to explain. Surprisingly, longer ownership appeared to be related to lower vehicle quality. The ratings of six of the nine vehicles on our list were well below the industry average in the JD Power 2012 Vehicle Dependability Survey.

The study measures problems experienced during the past 12 months by original owners of three-year-old vehicles (2009 model-year). In fact, Chrysler, Dodge, Infiniti and Jaguar were at the very bottom of the list.

Perhaps as a result of poor vehicle quality, drivers who own vehicles for a long period often switch makes when the cars are traded in. While 49% of people who turned in cars in the United States traded them in for the same brand, owners of seven cars on our list did so less often, JD Power customer retention data show. Less than 40% of Buick, Dodge, Chrysler, Volvo and Jaguar owners traded in their cars for the same make.

Taken together, the data create a puzzle. That may be because the car brands that people have owned for six or seven years are very different from those same brands today. Volvo is very nearly gone altogether, having withered since it was sold by Ford. Virtually every car in the Lincoln line is different from the ones it made seven years ago. Chrysler and its Dodge division have a new owner, as does Jaguar. Many of these brands and their new parents have launched cars to bring in younger buyers.

Based on data provided by Edmunds.com, 24/7 Wall St. identified the nine car makes whose owners held them six years or more before trading them in, measured as of October 2012. We also reviewed year-over-year sales and market share data as of October 2012, as well as the average number of days vehicles are in dealer inventory before they are sold during September 2012, all provided by Edmunds.com.

And we considered the average age of car buyers by make from Polk, as well as customer retention and vehicle dependability data from JD Power and Associates.